[Support] Add unit test for printLowerCase

Add test case for the function added in r319171.

llvm-svn: 319177
diff --git a/llvm/unittests/ADT/StringExtrasTest.cpp b/llvm/unittests/ADT/StringExtrasTest.cpp
index 234a40d..7bcdaf6 100644
--- a/llvm/unittests/ADT/StringExtrasTest.cpp
+++ b/llvm/unittests/ADT/StringExtrasTest.cpp
@@ -8,6 +8,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ADT/StringExtras.h"
+#include "llvm/Support/raw_ostream.h"
 #include "gtest/gtest.h"
 
 using namespace llvm;
@@ -84,3 +85,10 @@
   EXPECT_FALSE(to_float("7.4 foo", F));
   EXPECT_FLOAT_EQ(4.7f, F); // F should be unchanged
 }
+
+TEST(StringExtrasTest, printLowerCase) {
+  std::string str;
+  raw_string_ostream OS(str);
+  printLowerCase("ABCdefg01234.,&!~`'}\"", OS);
+  EXPECT_EQ("abcdefg01234.,&!~`'}\"", OS.str());
+}